Image sensors comprising a plurality of image sensor elements (sometimes also referred to as pixels) are used in many applications, in particular digital cameras like still cameras, video cameras or also cameras integrated in other devices like laptop computers or cellular phones. In such image sensors, image sensor elements are often arranged in the form of an array, wherein the individual image sensor elements for example may be read out columnwise or linewise.
Frequently used image sensors include CCD (charged coupled device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors. Sensor elements of these types conventionally are insensitive to the wavelength of the light, i.e. insensitive to the color of the light. To obtain color information for an image, an array of color filters for the primary colors red, blue and green is arranged in a pattern, for example in a so-called Bayer pattern, in front of the sensor elements of the respective image sensor such that each sensor element effectively is sensitive only to one of the primary colors red, green and blue.
Such sensors are conventionally silicon-based sensors. As the fundamental bandgap of silicon is of the order of 1.1 eV corresponding to photon energies in the infrared range, in some applications a filter filtering out infrared light is additionally provided in front of a corresponding image sensor to prevent infrared radiation from modifying an image captured by the image sensor.